Saab Offers Supercruising Stealth to South Korea

Saab Offers Supercruising Stealth to South Korea
Aviation Week & Space Technology
07/07/2008 , page 32

South Korea's combat aircraft requirement draws out advanced proposals from Western fighter houses

A Saab proposal to co-develop a stealth fighter with South Korea is raising the prospect of an Asian-European aircraft emerging to compete with the Lockheed Martin F-35 Lightning.

The South Korean project to build an advanced combat aircraft alternatively offers to fund developments of the Eurofighter Typhoon or to help sustain Boeing's waning fighter business - but there is also a strong chance that the ambitious program will collapse into yet another F-35 order.

Saab is pitching a new design for a supercruising stealth fighter to South Korea, as well offering the possibility of joining the Gripen next-generation program (AW&ST June 30, p. 42).

Boeing is putting forward developments of the F-15, including reviving a 1990s concept without tail fins, and it has also offered a new fighter design.

EADS is pushing developments of the Typhoon beyond the Tranche 3 standard, and also flagging the opportunity of participating in its combat drone project. It may also have submitted a clean-sheet-of-paper fighter concept.

Lockheed Martin meanwhile is telling Seoul that the F-35 Lightning will meet its needs. That's not surprising, since it has no business interest in supporting South Korean ambitions to co-develop a stealth fighter, which would surely become an F-35 competitor.

The diverse range of offerings from the four manufacturers reflects uncertainty in South Korea itself over combat aircraft development. The air force wants an advanced fighter, but various factions in the government, industry and military are debating whether the country should fill that requirement by buying off the shelf or by taking part in development of a new aircraft or major derivative.

The country has two substantive fighter requirements, F-X Phase III for 60 aircraft and then F-XX for 120. It also has a parallel domestic stealth fighter development program, KFX. The F-XX requirement calls for fifth-generation aircraft, so the hope is that KFX will fill that need through a joint program between South Korean and foreign industry, with the latter carrying up to 30% of the development cost.

But KFX is up for review this month by the administration of new President Lee Myung-bak. It may be canceled or restricted to co-production or assembly of an existing aircraft, boosting Lockheed Martin's hopes of an order for the F-35. An intermediate possibility would be South Korean involvement in less advanced developments of current production aircraft.

The manufacturers presented their ideas at an air force seminar in Seoul on June 26.

Saab has circulated two series of designs for South Korea, for single and twin aircraft, recent iterations of which have been designated P305 and P306, respectively. Its presentation at the seminar showed only the twin-engine design, probably reflecting South Korean views on how large an aircraft is needed. The air force's Warfare Development Group has described the KFX as having a capability between that of the F-15 and F-16. By "capability" it must mean weight and thrust class, since a new stealth aircraft would be much more capable than even updates of the 1970s designs.

Saab gave no specifications for its design but the external weapons shown on a drawing suggested an aircraft length of 17-18 meters (56-59 ft.). Span is much less than the length, possibly about 12 meters. If those rough estimates are correct, then the Saab stealth fighter would be at least as large as the Typhoon.

Saab shows single- and tandem-seat versions of the design. Inlet configuration is similar to the F-22?s, and the tail fins are canted. The trailing edge of the main-plane is swept forward, again like the F-22's, but the leading edge looks significantly less swept. A gun is mounted abreast the left inlet duct.

The manufacturer promotes the aircraft as a balanced multirole design offering broadband stealth, supercruise, "range and endurance," integrated sensors, avionics and weapons, and situational awareness through the human-machine interface. It also claims attractive "low life-cycle cost, growth potential [and] exportability," while dismissing "extreme stealth" as "suitable for tailored platforms."

Internal weapons stowage seems to be limited, since Saab says the bays are optimized for the air superiority role, although it still describes the aircraft as multirole in high-threat scenarios. External stores would be carried for low-threat scenarios. One of the three bays is behind the pit and between the inlets, and the other two are in the lower corners of the fuselage under the wing.

With domestic development, "upgrades and changes to the aircraft can be implemented according to Republic of Korea Air Force priorities without interference by [the] seller?s government, etc.," Saab argues, in a clear jab at Lockheed Martin. Brig. Gen. Lee Hee-woo, head of the Warfare Development Group, is opposed to a South Korean order for the F-35, saying the inaccessibility of its software will deny "operational sovereignty" to the user.

Within South Korea, the defense ministry's Agency for Defense Development is the most gung-ho about KFX. It would have little to do if KFX were canceled, so it is lobbying for the project to fill the F-XX requirement and has already produced stealthy concept designs.

Perhaps surprisingly, Korea Aerospace Industry is far less keen on an advanced development. Apparently mindful of its technological limitations, it would like the government instead to order the proposed F-50 combat version of the T-50, its Gripen-sized supersonic trainer.

The T-50 was developed under the guidance of Lockheed Martin, using the F-16 planform. Holding out the hope of a later development that might satisfy the urge to advance domestic technology, Korea Aerospace is also showing a concept of a delta-wing F-50XL, an analog of the F-16XL that Lockheed Martin offered to the U.S. Air Force in 1982. But the F-50XL concept differs from the F-16XL in having a wing with a straight leading edge, rather than a cranked arrow, and it has canted tail fins.

Some politicians are in favor of the F-35 for the F-XX requirement, and it is clearly well placed because of its combination of capability and cost.

The F-50 seems a long shot. Air force Chief of Staff Kim Eun-ki says the immediate priority is to continue buying fighters in the class of the F-15K until neighboring countries begin acquiring fifth-generation fighters.

Hence Boeing's opportunity in pushing the F-15K, of which South Korea has already ordered 61. Boeing updated the F-15E to create the F-15K for F-X Phase I, added features again for Phase II, and now says the Phase III model would have a next-generation active electronically scanned radar, electronic warfare suite, and advanced memory and weapon systems.

The KFX would follow that, and Boeing seems to have shown the finless F-15 as a possible candidate for the advanced program. The advantage of such an aircraft would be lower radar reflections, weight and drag. Brad Jones, Boeing's KFX program manager, tells Aviation Week & Space Technology that the Super Hornet could also be offered for KFX, and he adds that Boeing has also proposed a completely new design.

Jones suggests, however, that given the cost and development timescale implications of an all-new fighter, the defense ministry will most probably pursue the development of an existing aircraft to meet the KFX requirement.

The F-35 is the main competitor for F-X Phase III, as well as a strong candidate for F-XX. The immediate need to keep buying aircraft in the F-15K-class does not necessarily exclude the F-35, which is significantly larger than the Typhoon, for example.

The EADS offering is an improved Typhoon. In its presentation, EADS suggests new interface technologies, further development of sensor fusion and sensor upgrades, among others.

An EADS representative says: "The EADS approach to KFX is based on an overarching partnership with the Republic of Korea [RoK] for the future combat air system capability development, including on the one hand RoK participation in the development of the Eurofighter future enhancements, and on the other the joint development of an unmanned combat air system, offering the perfect mix in terms of RoKAF future capability, program affordability and Korean industry workshare."

A top South Korean government think tank responsible for economic policy analysis judged the KFX economically not worthwhile in December 2007 and stood fast when ordered by the defense ministry to reconsider its view (AW&ST Feb. 11, p. 19). The new government under President Lee, whose defense policy is vague, stresses economic efficiency first and foremost.

According to an industry source, one of the foreign companies offering to participate has assessed the program cost at 10 trillion won ($9.5 billion).

A committee chaired by Defense Minister Lee Sang-hee will conduct this month's review.

The Agency for Defense Development has revealed successful ground tests on radar-absorbing material on a McDonnell Douglas F-4 fighter. The timing of the May announcement could be interpreted as an attempt to gain publicity for the country's advanced aerospace efforts, helping to keep the KFX alive.

It isn't clear whether the South Korean material is structural or a coating, nor, if it is a coating, whether it is a paint or a metallic compound.

The agency says it has been studying the material since 1999 and received good results from trials in an indoor test facility. The next step will be flight tests, which will be conducted "soon," it says.

Taiwan, whose technological capability is similar to South Korea's, tested an imported anti-radar material on an AIDC AT-3 jet trainer in 2001-03. The supplier was "an overseas Taiwanese man," local media reported.

The Korean agency also says it has acquired technology for stealth shaping and analysis. In a November presentation, it showed pictures of a 1/10 scale model in an indoor radar range.

The model represented the agency's K100 concept for a fighter that would resemble a twin-engined F-35 with a multifaceted nose.

The KFX project dates back to the South Korean Joint Chiefs of Staff's decision in November 2002 to acquire up to 120 fighters, which is the requirement known as F-XX. In 2004-06 it became the basis of the agency's fighter design study, which spawned two concepts, the K100 and K200, the latter being a twin-engined canard-delta fighter.

Like Japan's full-scale radar cross-section model tested in France in 2005, the model probably closely reflects the agency's ideas of what sort of aircraft it currently has in mind (AW&ST Feb. 11, p. 36).

LMAggie wrote:This may sound odd from me, but this is kind of exciting. I'm a sucker for new jets.

geogen wrote:Ob, thanks for posting this article.

IMO, if anyone can make a more economical, sufficient alternative co-developed defense need (at least for the next 10 yrs) it would be Swedish.

LMAggie wrote:This may sound odd from me, but this is kind of exciting. I'm a sucker for new jets.

dwightlooi wrote:I think that if they want to jointly develop a jet, an F-35 derivative beats a Gripen derivative or a clean sheet Swedish-Korean design. It'll be more capable, more affordable and it's development will take less time. If they can put their historical rivalry aside, they may even get Japan in on the same project. Both nations have an air-to-air bias for their fighter requirement.




The F-35 is a very capable A2A platform as is, but it can be better if a dedicated A2A variant is developed which sacrifices range and payload for speed, a tad more agility and greater stealth. Re-winging the F-35A, going to a pelican tail and adding an F-119 style 2D nozzle on an F-135/136 engine uprated to about 52,000 lbs thrust may just do it.

Obamanite wrote:
Hmm, your concept looks like the love child of the YF-23 and the F-35. I'm not sure that it is feasible, though, since we're talking about an entirely different wing and empenage for the same fuselage, which would wreack havoc on the VLO characteristics (you'd have to realign the fuselage's angles to reflect the different sweep angles, and god knows what the interaction of your new wings and tails with the rest of the airframe would be, not only from an aerodynamic point of view, but more importantly from an RCS perspective).

Also, why go for a 2D nozzle for the F135/136 when, for a single-engined aircraft, an axisymmetric TV nozzle would be a lot more effective?

geogen wrote:How many new F-22s could be purchased for the entire program cost of such a 4th F-35 mod? I say just go for that many more F-22s instead.

dwightlooi wrote:The F-35 is a very capable A2A platform as is, but it can be better if a dedicated A2A variant is developed which sacrifices range and payload for speed, a tad more agility and greater stealth. Re-winging the F-35A, going to a pelican tail and adding an F-119 style 2D nozzle on an F-135/136 engine uprated to about 52,000 lbs thrust may just do it.

Multi-functional nozzles can accommodate more than engine area control, providing thrust vectoring or thrust reversing. These special application nozzles are typically used to reduce the demands of the aircraft control surfaces, resulting in overall system improvements.